Occurrence of Aikinite (PbCuBiS3) in the Sulphide-Rich Auriferous Quartz Veins of the Amphibolite Body of Perma Area, North-Western Benin Republic, Pan African Dahomeyides Orogenic Belt

Abstract

Aikinite (PbCuBiS3) is an uncommon mineral that belongs to the sulphosalt sub-set of the sulphide family with the general formula A2BX3, where A is a metal, B is a semi-metal, and X is sulphur. The mineral occurs mainly in hydrothermal mineral deposits. Although the mineral is principally reported from hydrothermal copper, gold, silver, molybdenum or polymetallic sulphide deposits in different continents, its occurrence in the African continent is fairly rare. Here, we report the occurrence and characteristics of Aikinite in quartz veins of amphibolite bodies from the Perma area (Republic of Benin), which belong to the external zone of the Pan-African Dahomeyides Orogenic Belt (PADOB). The mineral occurs in association with gold mineralisation, and the average chemical composition (Pb=35.76%; Cu=11.03%; Bi=36.20%; S=16.31%) of the studied sulphosalt is very close to the theoretical composition of aikinite with some Fe (0.31%) and Sb (0.05%) impurities. It has precipitated as inclusions within pyrite crystals of the quartz veins and co-occurs with gold, galena, chalcopyrite, barite, and Fe-rich dolomite. The studied aikinite is believed to have formed in a magmatic-hydrothermal environment at a temperature range of 260 to 270 degrees C.